package com.lhyl.front.web.shiro.filter;

import org.apache.shiro.cache.Cache;
import org.apache.shiro.cache.CacheManager;
import org.apache.shiro.session.Session;
import org.apache.shiro.session.mgt.DefaultSessionKey;
import org.apache.shiro.session.mgt.SessionManager;
import org.apache.shiro.subject.Subject;
import org.apache.shiro.web.filter.AccessControlFilter;
import org.apache.shiro.web.util.WebUtils;

import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import java.io.Serializable;
import java.util.Deque;
import java.util.LinkedList;

/**
 * 并发登陆人数控制
 * KickoutSessionControlFilter.java
 * <p>Copyright: Copyright (c) 2015 <p> 
 * <p>Company: xinghuo</p>
 *  @author    SeanXiao
 *  @version   1.0
 */
public class KickoutSessionControlFilter extends AccessControlFilter
{

    // 踢出后到的地址
    private String kickoutUrl;

    // 踢出之前登录的/之后登录的用户 默认踢出之前登录的用户
    private boolean kickoutAfter = false;

    // 同一个帐号最大会话数 默认1
    private int maxSession = 1;

    private SessionManager sessionManager;

    private Cache<String, Deque<Serializable>> cache;

    public void setKickoutUrl(String kickoutUrl)
    {
        this.kickoutUrl = kickoutUrl;
    }

    public void setKickoutAfter(boolean kickoutAfter)
    {
        this.kickoutAfter = kickoutAfter;
    }

    public void setMaxSession(int maxSession)
    {
        this.maxSession = maxSession;
    }

    public void setSessionManager(SessionManager sessionManager)
    {
        this.sessionManager = sessionManager;
    }

    public void setCacheManager(CacheManager cacheManager)
    {
        this.cache = cacheManager.getCache("shiro-kickout-session");
    }

    @Override
    protected boolean isAccessAllowed(ServletRequest request, ServletResponse response, Object mappedValue)
            throws Exception
    {
        return false;
    }

    @Override
    protected boolean onAccessDenied(ServletRequest request, ServletResponse response) throws Exception
    {
        Subject subject = getSubject(request, response);
        if (!subject.isAuthenticated() && !subject.isRemembered())
        {

            // 如果没有登录，直接进行之后的流程
            return true;
        }

        Session session = subject.getSession();
        String username = (String) subject.getPrincipal();
        Serializable sessionId = session.getId();

        // 同步控制，同一个用户被多处并发登陆的可能很小，这里暂时不做同步锁
        // synchronized (this.cache) {
            Deque<Serializable> deque = cache.get(username);
            if (deque == null)
            {
                deque = new LinkedList<Serializable>();
                cache.put(username, deque);
            }
    
            // 如果队列里没有此sessionId，且用户没有被踢出；放入队列
            if (!deque.contains(sessionId) && session.getAttribute("kickout") == null)
            {
                deque.push(sessionId);
            }
    
            // 如果队列里的sessionId数超出最大会话数，开始踢人
            while (deque.size() > maxSession)
            {
                Serializable kickoutSessionId = null;
                if (kickoutAfter)
                { 
                    // 如果踢出后者
                    kickoutSessionId = deque.removeFirst();
                }
                else
                { 
                    // 否则踢出前者
                    kickoutSessionId = deque.removeLast();
                }
                try
                {
                    Session kickoutSession = sessionManager.getSession(new DefaultSessionKey(kickoutSessionId));
                    if (kickoutSession != null)
                    {
                        // 设置会话的kickout属性表示踢出了
                        kickoutSession.setAttribute("kickout", true);
                    }
                }
                catch (Exception e)
                {
                    // ignore exception
                }
            }
    
            // 如果被踢出了，直接退出，重定向到踢出后的地址
            if (null != session.getAttribute("kickout"))
            {
                // 会话被踢出了
                try
                {
                    subject.logout();
                }
                catch (Exception e)
                { 
                    // ignore
                }
                
                saveRequest(request);
                WebUtils.issueRedirect(request, response, kickoutUrl);
                
                return false;
            }
    
            return true;
        }
    // }
}
